As specified here:

* https://docs.python.org/2/library/stdtypes.html#sequence-types-str-unicode-list-tuple-bytearray-buffer-xrange

This commit only uses the sequence count method for `list.count`,
but it can easily be applied to other sequence types in follow-on
commits.

Slight punctuation and hyphenation improvements, with additional styling on command and directory names.

In the course of reviewing #116 it came to light that
some of the other `str` methods that involve changing
case do not handle multi-byte characters correctly.
This patch fixes that.

Replaced FunctionArg with Param and moved arg validation logic out of
Code and into new ParamSpec type. ParamSpec can then be made more
general purpose and used for builtin functions.

Rather than allocating a frame on every call, we keep an already allocated list
of frames ready to go. This trades lightly more memory usage for faster calls.

Also updated Makefile to include these tests in the "make test" suite.
It became awkward to automatically detect the .py test files (they don't
really follow any particular naming convention) so they're listed
explicitly. To make things easier to follow I also listed out the other
stdlib test files explicitly. Long term I think we should be listing all
files this way (including .go sources) so that things are less magical.

* ToInt() function that dispatches to `__int__` slot
* ToIntValue() that does the above and then tries to fit it into a plain `int`
* Switch some functions that were doing IntType.Call() to these functions which fixed some unsafe conversions

pip install --upgrade flake8  # http://flake8.pycqa.org
python2 -m flake8 . --exclude=third_party --ignore=E1,E306 --max-line-length=80